Xbox 360 E 73 Error

OK this is my problem i bought a xbox 360 on craiglist for 70 bucks person told me it was just the reader and i fixed it by flashing it. i would have sent it in but the seal was broken on it. Now when i went and got a hard drive the system started freezing on me with a e71 error so i return the hard drive and got a new one. Now i got the system started and did a update to get my gamertag now i have the e 73 error. can any one help me.

E73: General Hardware Error: Ethernet port... this error is caused by a problem with the Ethernet port.Go to this website:
http://forums.xbox-scene.com/index.php?showtopic=484726It has a step by step on how to clear errors and reset your machine.